Treatment of cellulose prior to esterification



Patented July 26, 1932 UNITED STATES HENRY DREYFUS OF LONDON, ENGLAND TREATMENT or CELLULQSE r3103 To ESTERIFIGATION f i No Drawing. Original application filed'April 18, 1923, Serial No. 633,016, and in Great Britain May 24,

1922. Divided and this application filed July 28, 1927. Serial No.- 209,191.

This application is a division of my prior application Serial No. 633,016'filed April 18,

1923 which eventuated into Patent 1,708,787

issued April 9, 1929.

, The above application covers esterifying cellulose or its near conversion products with acetic or other fatty acid anhydride in presence of sulphuric acid or other strongcondensing agent to produce a highly viscous product by means of usingacetic acid or other solvent in quantity over 6 times the weight of the cellulose.

The subject matter of the present application relates toa preliminary treatment which may be given the cellulose 0r cellulose conversion products in order to render them more reactive to the esterification process while substantially preserving strength of the cellulosic material. While cellulose or its conversion products which have been pretreated according to the process hereinafter described and claimed are especially suitable for esterification according to the process disclosed and claimed in said parent application, nevertheless they may be esterified by other known or new processes of esterification.

To carry out the invention one can treat the cellulose such as cotton or conversion product of cellulose with formic acid alone, either with heating or at ordinary temperature, or with cooling, but preferably at ordinary temperature or slightly higher.

Such a special pretreatment may also be carried out by treating the cellulose or cellulose conversion product by heating or boiling with concentrated or dilute formic acid, preferably with the addition of small quantities of sodium acetate or other suitable neutralizin a ent which is ca able of neutralizin b b i any traces of mineral acids that may be pres? ent, and which mineral acid would have a destructive effect upon the cellulose mole cules, especially during the hot treatment with formic acid. The cellulosic material may be treated either in the cold or hot with concentrated or dilute formic acid, preferably but not necessarily containing a small quantity of sodium acetate or other suitable neutralizing agent. The temperature and the the 1 though may be employed in a concentrated form, this is less advantageous and it is bet- 3m 1 .ter to use a more dilute acid of about 100 C. or at the boiling point of the acid, the

treatment lasting about one to six hours,

more or less, and being correspondingly longer at temperatures between about and C. Similarly, with moredilute acid, such as acetic acid of from 80% to 50% I strength or less, the hot treatment will take correspondingly longerfor a given temperature dependent upon the increased dilution of the acid. 7 When formic acid is used, however, al-

strength or upwards. This will eifect the pretreatment more quickly even than a more concentrated acetic acid, and especially it is in this case advantageous to employ it in the cold. When a more dilute acid is used, a hot treatment is preferably adopted.

In any of the forms of pretreatment above described, the formic acid employed maybe used in admixture with diluents which are g not capable of entering into reaction with either the cellulose or the acid, such as toluol. This is found to be somewhat less advantageous.

The pretreated material may be subjected 5 directly to the esterifying reaction, but it found preferable to wash and dry the .same before subjecting itto esterification.

When cellulose or its conversion products are thus pretreated, the esterificationprocess {as is carried out more quickly, and it is possible,

-whenusing sulphuric acid or other strong condensing agent, to conduct andfinish acetylation at temperatures as low as 0 C. oreven lower. Of course since the esterificatio-n 're- 5335 action with such pretreated material is much more effective, higher temperatures may be employed by using increasedlquantities of acetic acid or diluent inthe esterification process. Thus, the esterification may be per-. 500

ately higher temperaturesare necessary.

Although of particularvalue in the production of cellulose acetate, the pretreatment which forms the subject matter of the present invention is of value in the production of any of the fatty acid esters of cellulose. The invention is, therefore, to be regarded as limited only by the scope of the appended claims.

What I claim and desire to secure by Letters Patent is 1. A process for pretreating cellulose, which comprises subjecting it to the action of formic acid in the absence of a condensing agent, thereby rendering the cellulose capable of rapid esterification.

, 2. A process for vpretreating cellulose, which comprises subjecting it to the action of formic acid of not less than 50% concentration in the absence of a condensing agent, thereby rendering the cellulose capable of rapid esterification.

3. A process for '45. A process for treatmg cellulose, which comprises pretreating it with formlc acid to render the cellulose capable of rapid esteri- .fication, removing the formic acid from the treating cellulose, which comprises pretreating 1t wlth formic acid to 10. A process for pretreating cellulose, which comprises subjecting it to the action of formic acid of not less than 50% concentration and containing a small quantity of comprises pretreating it with a concentrated formic acid to render the cellulose capable of rapid esterification, and afterwards subjecting it to the action of an esterifying medium.

13. A process for treating cellulose, which comprises'pretrea-ting it with a concentrated formic acid to render the cellulose capable of rapid esterification, and afterwards subjecting it to the action of an acetylating medium.

In testimony whereof I have hereunto subscribed my name. 1 I

HENRY DREYFUS.

cellulose, and afterwards subjecting, the cellulose to the actlon ofan esterifying'medium. 5. A process for treating cellulose, which comprises pretreating itwith formic acid to render the cellulose capable of rapid esterificatiomand afterwards subjecting it to the action of an acetylating medium.

6. A process for treating cellulose, which comprises pretreating it with formic acid to render the cellulose capable of rapid esteri- "fication, removing the formic acid from the cellulose, and afterwards subjecting the cellulose to the action of an acetylating :me-

dium. in 7 7. A process for pretreating cellulose,

which comprises subjecting it to the action of formicacid in the absence of a condensing agent to the cellulose and the acid, thereby rendering the cellulose capable of rapid esterification. p p p g 8. A process for pretreat of formic acid containing a small, quantity of a neutralizing agent for mineral acid, thereby rendering thecellulose capable of rapid esterification.

9. A process for pretreating cellulose,

awhich; comprises subjecting it'to the action andin the presence of a diluent inert ing cellulose, I 7 which comprises subjecting it to the action 

